This invention relates to an Auger electron spectrometer for analyzing a surface of an object by Auger electrons known in the art. More particularly, this invention is applicable to an electron gun for use in the Auger electron spectrometer so as to radiate an electron beam onto the surface.
In general, the electron gun has an electron gun axis extended to the surface and comprises an electron beam source for generating the electron beam along the electron gun axis and an electron lens system between the electron beam source and the surface on which the electron beam is incident along the electron gun axis.
In a conventional Auger electron spectrometer, the electron lens system comprises either only electrostatic lenses or only electromagnetic lenses. The electromagnetic lenses comprise coils which are often called coil excited electron lenses. When the electron gun comprises only the electrostatic lenses, the electron beam has a wide diameter on the surface because each electrostatic lens has a large spherical aberration. This adversely affects resolution of the analysis. When the electron gun comprises only the coil excited electron lenses, the electron beam also has a wide diameter on the surface because the coil excited electron lenses have a very large overall size. Furthermore, it is impossible to achieve a sufficiently low pressure for analysis because the coil excited electron lenses release a large amount of gas. The coil excited electron lenses have a considerably strong leakage magnetic field because each coil excited electron lens comprises a coil and/or a magnetic pole piece of a large size.